How the subsequent ordinary assessment works in Basel-Stadt
On a B permit, your employer deducts tax at source from your salary every month. Often that is the end of it. In certain cases, though, Basel-Stadt still wants a tax return from you. The procedure is called the subsequent ordinary assessment (nachträgliche ordentliche Veranlagung, NOV).
You then fill in a normal tax return. The tax administration calculates your tax with the actual federal, cantonal and municipal rates and with your deductions. The tax at source already deducted is credited without interest (§ 94 Abs. 6 StG BS). The Basel-Stadt form says openly that the result can be lower or higher than what you paid at source.
The basic rules apply across Switzerland. How the other cantons draw their lines is in our overview of the canton thresholds. This article covers Basel-Stadt for the tax year 2026, checked in October 2026.
Who has to file a tax return in Basel-Stadt
The subsequent ordinary assessment is mandatory for you if one of these applies:
- Salary of CHF 120,000 or more. Your gross salary from employment is at least CHF 120,000 in a tax year (§ 82a Abs. 1 StV BS, based on Art. 9 of the federal ordinance on tax at source).
- Interest and dividends of CHF 500 or more. Your capital income from movable assets reaches CHF 500 in the year.
- Assets above the allowance. Your assets are above CHF 75,000, or above CHF 150,000 as a married couple.
- Other income not taxed at source. For example from freelance work, pensions, maintenance payments or property. Basel-Stadt sets no minimum for this.
On the salary line, three points matter in practice:
- Married couples. The two salaries are not added together. If one of you reaches CHF 120,000, you are both assessed together (§ 82a Abs. 3 StV BS, § 94 Abs. 3 StG BS).
- Moving in or out during the year. Your regular salary is scaled up to twelve months for this test. One off payments such as a bonus count in full but are not scaled up (§ 82a Abs. 5 StV BS with § 40 Abs. 3 StG BS).
- Exactly CHF 120,000. The Basel-Stadt guide on tax at source 2026 says "more than CHF 120,000", while the ordinance says "at least CHF 120,000". The ordinance is what counts. The difference only matters if your salary sits exactly on the line.
Worth knowing for later: the subsequent ordinary assessment applies until tax at source ends for you (§ 94 Abs. 5 StG BS). Once you are in, you file every year, even if you no longer cross any line the following year.
The Basel-Stadt thresholds 2026 and their sources
| What counts | Single | Married | Source |
|---|---|---|---|
| Gross salary | CHF 120,000 or more | CHF 120,000 or more, per person | § 82a Abs. 1 and 3 StV BS |
| Capital income (interest, dividends) | CHF 500 or more a year | CHF 500 or more a year | NOV form 330-19016.a.01.26, reasons section |
| Assets | Above the allowance of CHF 75,000 | Above the allowance of CHF 150,000 | NOV form 330-19016.a.01.26, reasons section |
| Other income not taxed at source | No minimum stated | No minimum stated | NOV form; guide on tax at source 2026, p. 5 |
Tax year 2026, checked in October 2026. Sources (in German): application for the subsequent ordinary assessment, form 330-19016.a.01.26 (also printed in the guide and tariffs for tax at source 2026), the Basel-Stadt tax ordinance (SG 640.110) and the Basel-Stadt tax act (SG 640.100).
In our translation, the form puts the two cantonal limits like this: for income tax, capital income from movable assets below CHF 500 a year is exempt. For wealth tax, the form refers to the statutory allowances of CHF 150,000 for married people and CHF 75,000 for everyone else, which are not subject to wealth tax.
These allowances are set out in § 49 StG BS. There they are deducted from your net assets, meaning your assets after debts, based on the situation at the end of the tax year. The act also has its own amounts for single parents and for minor children, which the form does not mention. If you are a single parent or have children, we clarify case by case which limit applies to you.
One more detail in the wording: the tax act speaks of assets "and" income not taxed at source (§ 94 Abs. 1 lit. b StG BS). The guide and the form say "or". Going by the form, one of the two is enough.
Example from Basel-Stadt
Ana is single with no children, lives in Basel and earns CHF 92,000 gross. She holds ETFs and a savings account worth CHF 60,000 together, with no debts. Her interest and dividends come to CHF 650 in 2026.
- Salary: CHF 92,000 is below CHF 120,000. No obligation from that.
- Assets: CHF 60,000 is below the CHF 75,000 allowance. No obligation from that either.
- Capital income: CHF 650 is above CHF 500. That makes a tax return for 2026 mandatory.
Ana has to submit the form to the tax administration by 31 March 2027. From then on she files a tax return every year until tax at source ends for her. In Basel-Stadt, even a small portfolio can be enough to make tax at source no longer final.
Application, form and deadline in Basel-Stadt
In Basel-Stadt both routes use the same form, the "Antrag auf nachträgliche ordentliche Veranlagung (NOV)": the mandatory case because of assets or income not taxed at source (first box) and the voluntary application (second box). You can find it as a PDF and as an online form on the page applications and certificates for people taxed at source (in German). A form specifically for the tax year 2026 is not online yet (as at October 2026); the latest edition is the one for the tax year 2025.
There is no box on the form for the CHF 120,000 salary line. The tax act only requires you to ask for the form when you have assets or income not taxed at source (§ 94 Abs. 4 StG BS). If your salary was above the line and nothing arrives from the tax administration in spring, ask them.
- Deadline 31 March. The form must reach the tax administration by 31 March of the following year, so by 31 March 2027 for the tax year 2026 (§ 94 Abs. 4 and § 94a Abs. 3 StG BS). The version printed in the guide states that this deadline cannot be extended.
- Couples both sign. The form requires this explicitly.
- Moving abroad. If you leave Switzerland, the deadline for the application ends when you deregister (§ 94a Abs. 3 StG BS).
The office in charge is the Steuerverwaltung Basel-Stadt, Fischmarkt 10, 4001 Basel, email quellensteuer@bs.ch, phone 061 267 98 14.
The deadline for filing the tax return itself is a different matter. Our overview of tax return deadlines 2026 by canton has the details.
Opting in voluntarily: is it worth it?
If none of the lines applies, you can still apply for the ordinary assessment. There are no conditions (guide on tax at source 2026, p. 5; § 94a Abs. 1 StG BS). It is interesting if you have deductions the monthly deduction ignores, such as pillar 3a contributions. The numbers are in our article on pillar 3a with a B permit.
Before you sign, two points:
- No way back. You can only apply once, and you cannot withdraw it. After that you are assessed every year until tax at source ends for you (§ 94a Abs. 5 StG BS, NOV form).
- The result can be higher. The form itself points out that the ordinary assessment can lead to a lower or a higher tax bill than tax at source.
Whether the step pays off depends on your deductions and your plans for the next few years. We are happy to run the numbers with you.
Did you miss an obligation?
If your interest and dividends were already CHF 500 or more in earlier years and you never submitted the form, it is better to raise it yourself. We look at which years are affected and how to proceed.
We can also take care of the whole tax return for you. More on our page about tax advisory in Basel.